Factor Assays

Mixing Studies and Factor Assays

George is attending the International Society for Laboratory Hematology in Chicago, where he was presented a follow-up mixing studies question that was provoked by excellent discussions led by Drs. Mary Robinson and Dorothy Adcock of Esoterix Coagulation. The questioner performs a 1:1 mixing study using NP, and if it corrects, follows up with a mixing […]

More on Prekallikrein Deficiency

Here is an comment on Tracy Dixon’s prekallikrein deficiency case from Dr. Tom Exner, Haematex, Sydney, Australia. Hi, George, thanks for the interesting case; from Australia of all places! I’ve written up a couple of such cases many years ago. PKK and HMWK-deficient plasmas may be less readily available these days but the antibodies are […]

Prekallikrein Deficiency

From Tracy Dixon, Western Australia Department of Health. Hi George, We have a case currently of an elderly man with metastatic melanoma and liver involvment who is giving us a consistently long APTT (PTT) with a silica reagent, often >200 seconds. Prolonged incubation with the silica reagent has shortened this to around 60 seconds. The […]

Bethesda Titer

Cassandra McGeachy, Louisiana Coagulation, asks, I am trying to evaluate a set of FVIII inhibitor results and I am not sure what to call it. My patient + normal pool on my Bethesda assay yields a 23% FVIII and the next 4 serial dilutions bounce around between 15 to 19% instead of giving a higher […]

Bleeding Disorders

Unexplained Prolonged PTT

From Dr. Samir Patel: George, I have enjoyed reading the blog for many years now (since fellowship) and am wondering if you could shed some light on a patient I am working up. This is a 90 year old woman who was sent for evaluation after she developed a hematoma post cardiac catheterization (no need […]

Coagulation Factors

Combined IX and XII Deficiency?

From Dr. Jeanine Walenga, Loyola University Medical Center: George, what could be the reason(s) for a 30 yo female patient having multiple mild factor deficiencies of FIX (64%) and FXII (51%)? The activated partial thromboplastin time (APTT, PTT) was slightly prolonged but corrected with a mixing study. FVIII and FXI were normal. Patient does not have LA […]

What is an LDT?

From Kelly Townsend, Tri-core Reference Laboratories, Albuquerque. Looking for opinions on what constitutes a “Laboratory Developed Test” in Coag. Obviously if the reagent kit is not FDA-cleared, it will be an LDT, but what about factor assays, etc where there is no real kit. What if you are using a kit with a different calibrator or control […]

5 M Urea for Factor XIII

From Pam Owens: Hi George, good to see you at THSNA! (Thrombosis and Hemostasis Summit of North America). I am hearing more about how ineffective the 5M urea test is for factor XIII screening and am thinking we just need to stop doing the assay in our lab. I’ll need to convince our lab director. Are there any articles or published […]

Factor VIII Inhibitor?

From Deborah Whetzel, Children’s Hospital of the King’s Daughters, Norfolk, VA: We’ve had a couple patients lately that demonstrated inhibition but their factor VIII results are within normal limits or even elevated. The result values differ 30–40% typically between dilutions but as they’re diluted more, the values go up to 300 or 400%. FVIII values that high […]

Bleeding Disorders

“Backwards” FVIII Dilutions

From Kim Kinney, Indiana University Health, Hi George! We have a severe hemophiliac with an 8BU inhibitor receiving ReFacto. Factor assays are high, but dilutions dilute backward! 367, 238, then 183, then 167 causing a CV flag. We have seen this before, but have never heard an explanation for the “backward” dilution affect. Can you shed light? […]

Coagulation Factors

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George Fritsma is a medical laboratory scientist, educator, and author. George is a member of the International Society on Thrombosis and Hemostasis, the International Society for Laboratory Hematology, and the American Society for Clinical Laboratory Science.

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